DRF 'AE' OK FOR ONE SET OF FEATURES BUT NOT ANOTHER

Does the math still fail if you select fewer features in the set to see if it works somehow? Or just select 1 and see if has same calculation failed message. I've actually never seen that before, and didn't know  GeoTolerance would throw this type of error

Still fails

Is there any difference in the way the AA cylinders have been measured compared to the AB cylinders?  Are they both auto-cylinders, both using the same tip / sensor, same measurement strategy, same number of hits etc?

Yes. Same tip, angle, auto-cyl ... same everything. These features are tapped so same thread pitch using spiral scan

The spiral scan and pitch might be the problem - especially if you're trying to report local size with the "circular cross sections" option.

Not reporting size for any tapped hole. AA holes are tapped too.

Funny thing is if I apply MMB to dat E, the error disappears. But thats not to print.

Are you able to share the routine, cad model and drawing (print)?  You can upload them here: https://sendit.hexagon.com/filedrop/~HPt7sc 

Sorry. ITAR restricted